Axial gap electrical machine

ABSTRACT

An axial gap electrical machine employs unique architecture to (1) overcome critical limits in the air gap at high speeds, while maintaining high torque performance at low speeds, while synergistically providing a geometry that withstands meets critical force concentration within these machines, (2) provides arrangements for cooling said machines using either a Pelletier effect or air fins, (3) “windings” that are produced as ribbon or stampings or laminates, that may be in some cases be arranged to optimize conductor and magnetic core density within the machine. Arrangements are also proposed for mounting the machines as wheels of a vehicle, to provide ease of removing and installing said motor.

[0001] CROSS REFERENCE TO RELATED APPLICATIONS: 60/293,388; 60/307,148.

[0002] STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT:NOT APPLICABLE

[0003] REFERENCE TO A MICRO FICHE APPENDIX: NOT APPLICABLE

BACKGROUND OF INVENTION

[0004] This invention relates to axial gap electrical machines, and moreparticularly relates to such machines employing Permanent magnets. Axialgap electrical machines have been proposed in the past. Several examplesare found in the background art. For example: Jermakian 6,137,203.,Williams 6,046,518., Jun 6,172,442., Kessinger 5,744,896., Hazelton6,140,734., Smith 6,181,048.

[0005] Although the electric machines described in the this backgroundart are useful for some applications, experience has shown that animproved axial gap machine can be created by departing from the designtechniques taught in such machines and following the principles taughtand claimed in this application.

SUMMARY

[0006] In view of these background references what would be useful is anaxial gap electrical machine that can improve both high speedperformance and low speed performance that depend on the air gap,adequate cooling for the machine, and provide a means to optimizeconductor and magnetic core cross sections to optimize machineperformance.

[0007] This invention is useful as an axial gap electric machine. Insuch an environment, the preferred embodiment includes a coil assemblydefining a first side and a second side.

[0008] Objects & Advantages

[0009] Some of the objects and advantages of the proposed axial gapelectrical machine are to provide a unique architecture to overcomecritical limits in the air gap at high speeds, while maintaining hightorque performance at low speeds. A related object and advantage is toprovide a geometry that meets critical force concentrations within thesemachines.

[0010] Another object and advantage of the machine is to provide awinding structure that both minimizes Hall effect losses in theconductor and a magnetic core while optimizing both the conductordensity and the core material density, maintaining a homogenous toroidalstructure around the periphery of the stator, allowing a broad range ofwinding configurations from a single structure.

[0011] Another object and advantage of the machine is a series of phaselagged oscillators that activate the windings in phased sequence, withpower angles adjusted to either create a motor or generatorconfiguration.

[0012] Yet other objects an advantages of the present invention areunique approaches to cooling the magnet structure of the machine whilein operation.

[0013] Yet another object and advantage of the machine is in a wheelmotor configuration, where the wheel is separately supported and sprungbut driven by a co-axial motor thereby reducing the unsprung mass of thewheel and also minimizing the distortion of the motor elements underwheel loads.

[0014] Another object and advantage of the proposed axial gap electricalmachines, provides arrangements for cooling said machines.

[0015] Yet another object and advantage of the present invention is toprovide a means for easy attachment and removal of said axial gapmachine used as a vehicle wheel.

BRIEF DESCRIPTION OF DRAWINGS

[0016]FIG. 1 is an illustration of a cross section of the axial gapmachine illustrating tapered cross section for the rotor sections andthe stator sections.

[0017]FIG. 2A is an illustration of adjoining conductors in a winding.Notably the sequence of cross sections of the down conductor and the upconductors are in the same direction unlike in conventional windingswhere subsequent layers of such ribbon conductors would be in oppositedirections in each winding.

[0018]FIG. 2B is an illustration of the new proposed windings where thestructure permits lagged arrangement for windings that are “universally”variable in width for a given pole size thereby allowing a variable size(and number) of windings. A conventional winding arrangement is shownfor comparison.

[0019]FIG. 2C is an illustration of a single turn of ribbon conductor inan embodiment of the proposed new windings illustrating the twist in theconductor.

[0020]FIG. 2D illustrates an embodiment for serial connection ofadjoining loops in the windings. They may be assembled as individualloops and connected using the insulator and conductor configuration suchthat the second end of a conductor makes electrical contact with thefirst end of the next conductor.

[0021]FIGS. 2E, 2F, 2G are illustrations of a single turn of ribbonconductor in an embodiment of the proposed new windings illustrating thetwist in the conductor with the gap shown on the non-working conductornear the axle.

[0022]FIGS. 2H, 2I illustrates several adjoining ribbon conductors thatare arranged here for parallel connection The conductors that need to beconnected are pinned and the others are slotted to avoid electricalcontact.. These illustrations show the conductors straight for claritybut they would normally be twisted except for a small section in themiddle of each non-working conductor.

[0023]FIG. 3A is an illustration of several laminates or layers ofconductors, each layer having radial conductors on selected sectionsbetween the core sections to complete the circuit as desired. The layersmay have multile layers as shown with the return conductor severallayers away using an intervening radial section. Pins are illustratedthat connect selected layers without contacting intervening layers.

[0024]FIG. 3B is an illustration of the connection with the pins thatcontact some layers. Apertures in other layers are large enough to avoidcontact.

[0025]FIG. 4 in an illustration of possible connections for the phaselagged occilators proposed for different windings both in the proposednew ribbon conductor windings and for conventional windings.

[0026]FIG. 5A is an illustration of separate bearings for the motor andthe wheel bearings with a flexible connection such as splines or leafsprings to transfer torque.

[0027]FIG. 5B is an illustration of leaf springs to convey the torquefrom the motor to the wheel.

[0028]FIG. 6 illustrates the bimettalic consteruction of the layers inthe laminates to induce heat flow in a desired directio neither towardsthe hub or towards the periphery contributing to adequate heatdessipation arrangements.

[0029]FIGS. 7, 8 illustrates the twist in the ribbon conductor on one ofthe non working sections. In the interest of clarity the workingconductors are shown linearly disposed towards the twisted non-workingsection and the other non-working section is not shown. In a nornmalworking configuration the two working conductors will be bent down to beoritented radially in the machine while the non-working conductors withthe twists follow circumfrancial arcs either near the axle or near theperiphery of the stator.

[0030]FIG. 9 illustrates an embodiment of the magnet assembly in thepresent invention. Each of the magnet sections are shown to be radiallyseparated into several peoices and bonded together to minimize eddycurrent losses. Further the illustrated embodiment has the magnetsections with air gaps between them for cooling. The magnet sections aresupported by minimal brackets (not shown ) that hold the magnets inrelative positions. However the centrifugal foreces are resisted by thehousing of the motor which supports the rotor. The gaps between themagnets may have a small pitch to induce airflow through the gaps in onedirecton. In some embodiments the magnet sections and the brackets maybe pivotally and/or slidably mounted for changing the air gap as notedherein. The magnet assembly in the illustrated embodiment is tapered tobe narrower torards the axis to allow air gap control as noted herein.

[0031]FIGS. 10, 11, 12 illustrates an embodiment of the invention whererigid ribbon working conductors and pressed or formed nonworkingconductors welded or otherwise attached to the working conductors may beused. The illustrated non-working conductors ( on one side ) conform tothe topological constraints for the double torroid construction of thisinvention with conductors in a single loop haaving working conductors intwo adjoining torroidal sets of conductors.

[0032]FIG. 13 illustrates another embodiment that has simplerarrangements for the non-working conductors but will result in workingconductors that are not disposed with their widths radially to minimizeeddy current losses. This illustration show a gap in the non-workingconductor at the inner axial end. These may be connected in series withadjoining lops or in parallel to adjoining loops the arrangements forthese are noted herein.

[0033]FIG. 14 illustrates the bimettalic construction of the conductingstrip to induce heat flow in towards the hub and to induce a coldjunction at the periphery. In the illustrated embodiment, there isairflow through the gaps between the magnets in each of the assemblythat is forced through the stator/rotor airgap and oever the edge of thestator and the cold junction. Thereby cooling the magnets. There isnormally a direct current superimposed on the working currents of themotor/generator to induce the thermo electric effects. In thisembodiment the axle may be cooled internally with coolant liquid orgasses.

[0034]FIG. 15 illustrates the bimettalic construction of the conductingstrip to induce heat flow out towards the periphery and to induce a coldjunction at the axle. In the illustrated embodiment, there is airflowthrough the gaps between the magnets in each of the assembly that isforced through the stator/rotor airgap and through ports in the statornear the axle for heat exchage with the cooled conductors. Therebycooling the magnets. There is normally a direct current superimposed onthe working currents of the motor/generator to induce the thermoelectric effects. Fins may be installed in the vicinity of the hotjunctions on the outer body of the rotor to cool the hot junction.

[0035]FIG. 16 illustrates a cut away view of an embodiment with multiplerotors and stators and a tapered rotor/stator construction.

[0036]FIG. 17 illustrates a bimetallic construction for a single loop ofthe stator windings.

[0037] LIST OF REFERENCE NUMBERS

[0038]101—Stator winding section tapered construction

[0039]102—Rotor Magnet assembly middle section—tapered construction

[0040]103—Rotor Magnet Assembly end section—tapered construction

[0041]104—Motor housing

[0042]105—Rotor Bearing

[0043]106—stator support axle.

[0044]107 A—First Ribbon conductor first Radial component (current intopaper)

[0045]107 B—First Ribbon conductor second radial component (current outof paper)

[0046]108 A—Second Ribbon conductor first Radial component (current intopaper)

[0047]108 B—Second Ribbon conductor second radial component (current outof paper)

[0048]109 A—Indicator—current out of paper

[0049]109 B—Indicator—Current into paper

[0050]110 A—Edge 1 of the ribbon conductor

[0051]110 B—Edge 2 of the ribbon conductor

[0052]111 A—Twist in center section of ribbon conductor

[0053]111 B—Twist in circuinfrancial section of ribbon conductor.

[0054]112—Open hole on this layer—no contact with pin

[0055]113—Closed/tight hole on this layer—electrical contact with pin

[0056]114—flexible peripheral wheel coupling

[0057]115—Wheel

[0058]116—Motor/generator Rotor

[0059]117—Motor/Generator Rotor bearing

[0060]118—Wheel bearing

[0061]119—leaf springs—torque transfer in tension

[0062]120—An inside single magnet element as part of a single magnetsection.

[0063]121—An edge single magnet element as part of a single magnetsection

[0064]122—The inside end of the magnet sector showing a narrower crosssection

[0065]123—working conductor—side 1 of torroidal coil

[0066]124—working conductor—side 2 of torroidal coil.

[0067]125—Non-working conductor that meets the topological constraintsfor this embodiment

[0068]126—Cold junction of the bimetallic construction of windings.

[0069]127 -Hot junction of the windings of the bi-metallic constructionof the windings.

[0070]128—Gap where loop is connected to adjoining loops at each endseries or parallel

[0071]129—Working conductor—metal 1

[0072]130—Working conductor—metal 2

[0073]131—bimetallic junction 1

[0074]132—bimetallic junction 2 (betwen adjoining loops)

DETAILED DESCRIPTION OF INVENTION

[0075] The proposed axial gap machine has a plurality of disk-likemagnet assemblies that constitute the rotor of the machine, that areinstalled to the outerbody of the machine. The outer body in turncompletes the magnetic circuit for the magnet assemblies, which providethe means for air gaps with axial magnetic fields. Moreover, one or moreof these rotor magnet assembly disks may be supported with bearings onthe axis to which the stator is fixed resulting in the assembled rotorresting on the central axle on a plurality of bearings that are mountedat the radially inner edge of two or more of the said magnet assembliesthat interleave the stator disks. Such an arrangement may be constructedfrom separate disk assemblies of magnets as in rotors of axial fieldmachines well disclosed in the background art, that are attachedtogether leaving adequate space between them for the required axial airgaps and a stator in each intervening space between adjoining rotormagnet assemblies.

[0076] The stator is composed of a plurality of disks that are eachcomposed of windings that are fixed to the central axis of the machine.Each of these disks are interspersed with the rotor disks as describedabove. The said axis also provides the support for a wheel in a vehicleor gear or pulley arrangements in machines.

[0077] According to another feature of the invention, coils for anelectric machine may be fabricated by conventional windings and cores orthe following means.

[0078] Windings may be composed of elements constructed in sectors of atorroid or annullar ring that interlock as follows: Each of theconductors are shaped to form a loop with open ends preferably at theouter circumferential edge of the torroidal or annular shape that isdescribed. The cross section of the conductor is of a ribbon with widthmuch greater than the thickness to minimize the Hall effect on theconductors. Magnetic core material of small cross section and inelements of length equal to the width of the ribbon may be attached tothe conduction ribbon on one or both sides with insulating film. Theconducting ribbon is of course insulated. The ribbon shaped conductormay be formed in many ways. One of the approaches are as follows: Theribbon shaped conductor is formed into a loop first without twisting theribbon (0 degrees twist ). The loop is further formed by straighteningtwo diametrically opposed edges to form the two radial sections at apredetermined angle to each other that define the sector of the torroidor annullar ring that a single loop of the winding will cover. However,one of these two radial sections of ribbon are twisted by 180 degreesand maintains this angular orientation along its entire length. Thisresults in the corresponding wide surface of the ribbon on both radialsections facing the same direction. This twist in the ribbon results inthe twist being entirely generated through 180 degrees at thecircumferential sections of the loop. Finally the two radial sectionsare placed so that they are radii of adjoining cylinders about the sameaxis. Stated another way, the circles of rotation of the two radialsections of the ribbon, develop two cylinders that are co axial andadjoining each other but do not intersect each other. This constructionof the loop allows a series of such loops to interlock with each otherto form a complete torroid or annullar ring without any gaps. Moreover,if the magnetic material is bonded to the ribbon this will form adistributed core as well. With this construction of interlockingribbons, the cross section of the torroid or annullar ring has tworibbon shaped conductors edge to edge one each fron the loops on eitherside of the torroid or annullar ring. Each of the independent loops haveterminals or simply flanges at each end of the ribbon loop positioned onthe inner or outer circumferential non-working section. Such flanges maybe connected in series or parallel to each of the phases of the powercircuits, to meet the particular winding need. Such connections may bemade with pins that connect selected flanges.. Notably, such a windingcan be universal except for the sector angle that is described by theloops, in that the individual loops can be connected to any number ofphases and turns per winding. A further improvement would be to useconductors of widening cross section on the radial sections to maximizethe conductor crossection in each loop. The ribbon may alternatively betwisted by 360 degrees from end to end of the loop (instead of a net 0degrees) by twisting each of the circumfrantial sections by 180 degreesin the same direction (rather than in opposite directions for the 0degrees net). In either of these arrangements, the optimal utilizationof the stator winding volume is achieved by adjusting the thickness ofthe conductors in relation to the thickness of the ferromagneticmaterial to maximize the flux linkage to the rotor by lowering thereluctance with more ferromagnetic core material while maximizing theconductor thickness and the current density. The conductor ribbons maybe stranded and or braided wire to be more flexible in this arrangement.In some embodiments the entire back shaped as an annular flat diskbetween the two sections of conductors provides additional rigidity tothe windings but is not physically connected to the axle. the similarembodiments may not have a backiron element at all and have the formendwindings (with interspersed core elements if used) support themselves asthe entire stator. The entire load is transferred through the materialof the windings to the axle. In other embodiments, the ribbon conductorsmay be either slotted on the inside circumfrancial sections or bentaround (at the sections of the ribbon that is twisted, at a point wherethe width is parallell to the radius) to accommodate radial elements ofthe supporting back iron that may lie between the concentric cylindersformed by the windings as noted above. The back iron may be radiallyserrated to accomidate the edges of the windings and bonded together bymethods well disclosed in the background art. Moreover, if the statorwindings are predefined at the time of assembly and the physical angleof each phase winding is known in advance, the back iron may have raisedsections that index the windings between these sections of the ribbonwindings to transfer torque during operation. In addition the ribbonconductors may be shaped to index the sides of the back iron disk. Yetother embodiments several selected adjacent sections of the ribbonwindings have broader cross sections in the radial (or working) sectionsof the ribbons thereby creating a set of splines that may interlock withsplines in the back iron to transfer torque.

[0079] The above winding arrangement may also be used in an embodimentwith the permanent magnet rotor fixed to the axle and the statorattached to the housing of the machine.

[0080] Several embodiments are possible with the windings in the currentinvention using topologically equivalent conductor shapes. For exampleindividual ribbon loops may be constructed to have two flanges near theaxial edge of the working conductors on each of the legs of the loop, sothat in the winding position these flanges of adjoining loops form aring around the axis of the machine that can be used for support andalso heat dissipation if they engage fixed elements of the axle.Moreover, such flanged may be arranged to be of varying lengths suchthat when assembled as a winding they form a splined profile that willbetter transfer torque to the axle.

[0081] Another application in using topologically equivalent conductorsto flat ribbon conductor loops is to fold the conductor at the non-working ends to reduce the edge length on one side and not the other soas to allow easier assembly of the the loops in the stator torroid. Yetanother topologically equivalent form is to have an“O” shaped flatribbon conductor (that may be stamped out) with straight sides thatcorrespond with the length of the working conductors of the loop andstraight conductors of the length of the non-working peripheral andaxial conductors respectively. The closed form needs to be cut andseparated at a point on the inner non-working conductor section toconnect with adjoining loops. Sections of the Non-working conductors canthen be bent to be perpendicular to the working conductors to permit theloop and winding configuration of the twisted conductor torroidconstruction noted in this invention with one notable difference—Thetorroid generated by these open loops that form the windings may nothave an axis perpendicular to the width of the conductor but be at anangle thereby compromising he eddy current loss characteristics and theairgap.

[0082] The above winding arrangements utilize the entire space in thetorroid or annullar ring with either conductors or magnetic corematerial. This is particularly so in embodiments where the radialconductors are made to be wider towards the outside of the coil.Furthermore it is possible to “grind” the windings or ribbons along withthe distributed core to have any desired cross section for the statorthereby optimizing the airgap that may follow a non- linear rotor crosssection as in some special rotor configurations noted in this invention.

[0083] Yet another embodiment will have the ribbon conductors packedwith powder metal and compacted with dynamic magnetic compaction orother techniques available in the background art. This will improve theefficiency of utilization of space between conductors for a lowerreluctance magnetic path. This is particularly useful if a constantthickness conductor is used and there is a greater gap between adjoiningconductors towards the outer end of the working conductors. Yet anotherfeature of this invention is an embodimen that has the radial sectionsof each ribbon conductor preformed and attached to a (insulating)membrane bag of the same shape as a side of each of the radial sectionsof the conductor, containing powder metal in a predetermined quantity.At the time of assembly of the coil, the powder metal will beredistributed in the thin membrane bags to take up all the availablespace between the conductors—more towards the outer ends of the radii.The assembly may then be compacted as noted above. Following theassembly of the windings as follows, the surface of the winding with theattached core material may be ground or machined to expose the surfaceof the ribbon conductor from the surrounding core material so that amagnetic gap is established to minimize magnetic leakage in the machine.

[0084] The present invention may use rotor disks with magnetsconstructed in the conventional aft manner as disclosed in thebackground art or use rotor disks that are tapered to be narrower at thecenter and broader and the periphery where they are attached to the bodyof the rotating shell, and wherein the stator disks are tapered to bebroader at the base at the axis and narrower towards the edge of thedisks. Thereby the geometry will ensure that of the taper rates are thesame for stator and the rotor, the airgap will remain the same radiallyacross the machine for all the disks. Moreover, as the greatesttorsional forces on the stator are near the axis and the greatesttortional forces on the rotor are near the periphery, this geometry canoptimize material usage to minimize weight of the machine for therequired strength characteristics.

[0085] An additional feature of the present invention with the abovetapered rotor design can be utilized to optimize the air gap fordifferent speeds for operation. A small air gap is desired in themachine at low speeds to maximize the torque generated by the machine.However as the machine builds speed, both back EMF and air resistance inthe air gap will limit the speed of the machine significantly. Thetapered design in the present invention can be adapted to automaticallyincrease the air gap at high speed . This can be a smooth gradualprocess that matches the gap for the speed of performance. This isachieved by moving the sections of the rotor radially outwards by a verysmall amount. Notably, by having different gradients of taper of thesides of the rotor radially, the rate of change of the airgap can bedifferent for different radial distances from the axis. For example, asthe relative linear velocity between the stator and the rotor at theperiphery of the motor rises more rapidly as the motor accelerates, agreater increase in air gap could be beneficial at the periphery. Thiscan be achieved by having a steeper taper at the periphery of the motor(rotor and stator) and a more gradual taper towards the center of themotor. The exact tapers can be designed using computer simulations ofthe effect of back EMF and turbulent flow in the airgap. This movementmay be achieved with centrifugal force on the rotor sections and specialfabrication of the radial magnet sections (and brackets if used) of therotor and the intervening mechanical connectors that may be springloaded to permit slight expansion circumferentially and a specialconstruction of the rotor with the bearings on the axle to permit aslight extension radially. Such an arrangement can “stretch” the outersupporting ring of the rotor under centrifugal force to increase the airgap with the above tapered design. The outer supporting ring can havespring loaded telescoping sections between the magnet supports, thatallow this increase in diameter under centrifugal force. The magnets(with radial support brackets if used) may be connected rigidly at theouter periphery but slidably at the inner end to a ring support that maybe attached to a bearing that support the magnet assembly particularlywith regard to axial movement.

[0086] Yet another approach for changing the airgap is to utilize thetorque generated in the machine to stretch elements of the rotor. Forexample if the sectors of the rotor are constructed as radial sectionsfag (for example for each pole section separated physically) andsupported pivotally at the center and the external to periphery by twoannular rings or other support (the inner supports must allow somemovement as well: such as with an elongated slotted pivot ), such thatwhen the sections are perfectly radial there is a larger gap between thead radial elements (not the working airgap between the rotor andstator). A twisting of the inner annular ring about if its axis, forcesthe “radial” magnet sections to move at a slight angle to the radial butincreases the radial distance at each point on the magnet from the axisby moving the slotted pivots slightly in their respective slots. Underlow load and no-load conditions the sectors of magnets are designed tobe at a small angle to the radial direction thereby increasing theworking airgap as a result of the tapered construction of the rotor andstators. However, under high load conditions the torque generated by themotor will drive the magnet sectors to a perfectly radial positionthereby reducing the working airgap and increasing the power deliveredby the machine and the torque generated against the load. The mountingarrangement will of course have to be spring mounted to resist thesechanges at low torque but allow this distortion at high torque. Thereshould also be an end stop device to prevent the rotor sections frommoving past the radial position to incline from the radial in theopposite direction to the no-load position under extreme load andthereby reducing the ability of the machine to provide adequate torqueas a result of the increase of the working air gap.

[0087] Yet another embodiment can use differential expansion of therotor with regard to the stator to increase the airgap at highertemperatures with the tapered design in the present invention. Each ofthe magnet structures that are positioned radially are connectedtogether circumfrantially and to the hub in the center by materials thathave a high coefficient of expansion with heat in addition to theirrequired load bearing properties required in this application. As thetemperature of the machine rises the expansion on the rotor of theconnecting elements between the magnets and the connecting elements tothe hub(s) is designed to exceed that of the expansion of the stator andas result of the tapered construction will cause an increase in the gapof the machine.

[0088] Yet another embodiment of this invention has a magnet rotorattached to the axle with the stator attached to the housing andcomprisig windings with a higher coefficient of expansion than themagnet assemblies, thereby increasing the air gap with the taperedrotor/stator arrangement.

[0089] Yet another embodiment utilizes the fact that the magnets need tobe supported to resist a tangential torque and a outward radialcentrifugal force while in operation. As the rotor is supported in theseembodiments by the motor body structure, the magnets in sectors may befixed on the outer circumfrancial edge and radial air gaps ( betweenradial sectors of magnets) pemitted between adjoining magnets with onlyminimal support with spacers or minimal brackets to support the magnetsto equalize torque between the magnets and reduce vibration. Theseradial airgaps contribute to the cooling of the magnets—a particularlyimportant factor in axial gap machines. The cooling can be furtherimproved by inclining the magnet faces between the magnets to be at asmall angle to the axial direction so that the gaps scoop air from oneside of the rotor and deposit it at the other side of the rotor. The Airreturn path could be at the periphery of the motor where cooling devicesmay be harnessed to lower the temperature of the air. The Air that isforced through the motor may be retuned to the other side of the motorafter cooling in tubes on the periphery of the motor or inducted on oneside of the motor and discharged on the other side of the motor. Thelatter arrangement will benefit more from a low ambient temperature butsuffer from the disadvantage of impurities in the air that may damage orimpair the motor operation. Some embodiments for such cooling follow inthe present invention. Notably the stator windings in adjoining sectionsalong the axis will need to be sqewed to ensure that the faces of themagnet line up with the rotor windings on both sides for the rotor (inthe event of stator windings being present on both sides for the rotormagnet). Still other embodiments have the radial sections fo the magnetssubdivided into smaller radial sections and interspersed with insulationthin film and pinned together to form each of the magnets that comprisethe set of magnets around the perimeter of the rotor. This constructionwill reduce the Hall effect heating and power loss in the magnetassemblies.

[0090] Yet another feature of this invention is the use of a number ofoscillators that are each phase lagged to one another, the set of saidoscillators together forming a complete 360 degree electrical phaseshift and may be driven off a controller (for example a hall effectcontroller) that identifies the position of the rotor for synchronizingthe set of oscillators. These oscillators are connected to each of thephases of the motor (or generator) The power angle, and frequency arecontrollable with large capacitors ( ultra capacitors may be used inthis application) thereby permitting control of power delivered orextracted in regenerative mode of the motor. This arrangement of thesequence of oscillators provide a mechanism for energy storage,deployment and retrieval in the sort term particularly useful in vehicledrive applications. The oscillators can be designed to deliversinusoidal waveforms or even what may approach square wave forms tomaximize the torque generation of each phase. The background art hasextensive material related to the use of controllers and sensors forcontrol of moving magnet rotor motors, in the design of phase laggedsystems of oscillators and power control of electrical machines bychanging the power angle and frequency control of electricaloscillators. Notably the torque generation of the motor may acceleratethe motor that in turn will require a higher frequency of oscillatoroutput. To continue torque generation.

[0091] Yet another embodiment has separate load bearing axial bearingsfor the wheel from the bearings of the motor, while the wheel and motorare coupled to convey torque along the periphery of the motor, therebyminimizing the radial compression of the motor due to loads that thevehicle bears and which are transmitted through the wheel bearings. Thiswill improve the performance of the tapered design for the motorelements as noted above by minimizing the change in axial gap withphysical loads on the vehicle and its wheels.

[0092] Special arrangements need to be made in this and otherarchitectures if there is a load supporting function for the presentinvention as in the use in a wheel structure for a vehicle. Load bearingfunctions as in wheels particularly on uneven surfaces, will causerelative compression of the rotor relative to the stator in the regionbelow the machine, if there is a rigid connection between the wheel andthe motor. Furthermore the unsprung mass of the wheel can be substantialif the motor is rigidly connected to the wheel. An alternativearchitecture in the present invention will be to have the load bearingbearings of the wheel separate to those of the motor itself and themotor shell attached flexibly to the wheel periphery to transfer torque.This may be done with tangential leaf springs that around the peripherymounted at one end to the wheel and at the other end to the motorhousing on its periphery and thereby indirectly attached to the rotor.In this arrangement for forward motion the leaf springs will be intension. These leaf springs may be designed to accommodate a compressiveload for reverse motion of ht e vehicle. Alternatively, a second set ofleaf springs may be used to be in tension when the vehicle is reversingand in compression in the forward direction. This second set of leafsprings may also be mounted at one end to have limited slidingcapability so that when the vehicle is moving forward, these springs arenot in compression but slide at the end coupling, but slide back toaccept the tensile load when the vehicle is in reverse. This limitedsliding arrangement may also be done for the first set of leaf springsto avoid compression when the vehicle is in reverse.

[0093] Another approach for the torque conversion in this architectureis to have key and slot arrangements along the periphery between thewheel and the motor. Compression of the wheel at any point on itsperiphery can be accommodated by the key sliding further into the slot.Torque will be transferred by the keys. The arrangement may have theslots on the wheel and the keys on the motor housing or with the slotson the motor and the keys on the wheel.

[0094] This new architectural feature may be taken further to haveinternal shock absorption for the wheel with flexible elements betweenthe wheel bearing and the wheel periphery, thereby protecting the motorfrom excessive shock in this application as a wheel motor and reducingfurther the unsprung mass of the wheel. For example heavy leaf springscan be mounted tangentially between the periphery of the wheel and thecentral part of the wheel that is connected to the bearing, these leafsprings will accommodate some deflection of the wheel periphery relativeto the bearing. In some embodiments of such internal shock absorbtionfor wheels magnetic bearings may be employed.

[0095] Another aspect of the present invention is that cooling of themachine can be achieved with one or more of the following means:

[0096] 1. In applications where the motor operates in dusty conditionsor in water, the motor may be cooled with air pumped through an axialhole in the axle of the motor through ports in the stator between therotor sections and forced out of the ports in the rotor. He pressuredifference can be designed to ensure that there is no water or dustentering the motor.

[0097] 2. In less severe conditions the motor casing can have fins verymuch like brake fms ion car wheels that scoop air into the motor throughports in the outer rotor disks each of the rotors and the stator disksinside the machine.

[0098] 3. Yet another approach is to use bimetallic conductor strips ineach of the loops of ribbons that are proposed in the windings such thata part of the loop is of one metal and the remaining part of that loopis of the other metal, thereby forcing a cool junction at the peripheryof the motor. The hot end can be designed to the axle which can bedesigned to be a heat sink to conduct heat to outside the motor. Thisarrangement can be combined with that descriebed earler with the rotormagnets with the inclined radial air gaps between the sector magnets,scooping air from the axial gap on one side of the rotor and depositingit on the other side and forcing a pressure diffential that drives theair over the periphery of the stator which is cooled using the coldjunction. The air may be returned alongsealed paths or inducted anddischarged to the atmosphere on the sides of the motor. If inducted anddischarged into the atmosphere it will benefit additionally from thelower ambient air temperature. The hot junction will be at the axis, andthe axle may be designed to be a heat sink to conduct heat out of themotor. In thse embodiments that use the bimettalic stators for coolingthere will of course be a direct current superimposed on the reversingcurrents (if required) to provide the cooling effect. The bimettalicwinding arrangement may also be constructed to have the cold junctionsand hot junctions in different locations, but such arrangemtns need tohave heat sink arrangements near the hot junctions and locate the coldjunctions where the magnets are cooled directly by convection throughthe air gap or cooled by an air flow that is forced around the coldjunction. For example some embodiments may have the cold junction at theaxis of the stator and fins at the periphery of the rotor to cool theouter edge of the airgap where the hot junction is located. Air can beforced through ports in the rotor bearings if such bearings are locatedbetween the stator sections.

[0099] By using the foregoing techniques, an electric machine can befabricated with improved efficiency and results in an electric machinehaving improved operating characteristics.

[0100] Considering that in an application of the present invention in avehicle wheel, ease of removal of the wheel and he motor are keybenefits, the present invention proposes a central attachment along thenon rotating axle for attachment with a central bolt that secures thewheel to the axle. The fit of the axle with the wheel socket for thispurpose, may be tapered to allow the tension in the bolt to increase thereaction force between the socket and the axle surface. Moreover, totransfer torque the socket and the axle contact surfaces may be splinedor keyed.

[0101] Furthermore this possible assembly aspect of the presentinvention may be further refined to have the wheel in two sections—theiner section that is on one side of the motor on the axle and outersection that is on the other side of the motor on the axle. Removal ofthe wheel without removal of the motor may be facilitated by removal ofthe external section only with the tire. The two sections of the wheelmay be held together under operating conditions by bolts or otherfasteners or simply key into each other when the rim and tire with theexternal section are installed to the axle. This keying arrangement mayalso be between the wheel rim attachments and the inner section.

PREFERRED EMBODIMENT

[0102] The following is a detailed description of some of the componentsof the preferred embodiment of the present invention.

[0103] The axial gap machine in the preferred embodiment has a pluralityof disk-like magnet assemblies that constitute the rotor of the machine,that are installed to the outerbody of the machine. The outer body inturn completes the magnetic circuit for the magnet assemblies, whichprovide the means for air gaps with axial magnetic fields. Moreover, oneor more of these rotor magnet assembly disks may be supported withbearings on the axis to which the stator is fixed resulting in theassembled rotor resting on the central axle on a plurality of bearingsthat are mounted at the radially inner edge of two or more of the saidmagnet assemblies that interleave the stator disks. Such an arrangementmay be constructed from separate disk assemblies of magnets as in rotorsof axial field machines—well disclosed in the background art, that areattached together leaving adequate space between them for the requiredaxial air gaps and a stator in each intervening space between adjoiningrotor magnet assemblies.

[0104] The stator is composed of one or more disks that are eachcomposed of windings that are fixed to the central axis of the machine.Each of these disks are interspersed with the rotor disks as describedabove. The said axis also provides the support for a wheel in a vehicleor gear or pulley arrangements in machines.

[0105] According to another feature of the invention, coils for anelectric machine may be fabricated by conventional windings and cores orthe following means.

[0106] Windings are composed of elements constructed in sectors of atorroid or annullar ring that interlock as follows: Each of theconductors are shaped to form a loop with open ends at the innercircumferential edge of the torroidal or annular shape that isdescribed. The cross section of the conductor is of a ribbon with widthmuch greater than the thickness to minimize the Hall effect on theconductors. Magnetic core material of small cross section and inelements of length equal to the width of the ribbon may be attached tothe conduction ribbon on one or both sides with insulating film. Theconducting ribbon is of course insulated. The ribbon shaped conductormay be formed in many ways. One of the approaches are as follows: Theribbon shaped conductor is formed into a loop first without twisting theribbon (0 degrees twist ). The loop is further formed by straighteningtwo diametrically opposed edges to form the two radial sections at apredetermined angle to each other that define the sector of the torroidor annullar ring about the axis of the machine that a single loop of thewinding will cover. However, one of these two radial sections of ribbonare twisted by 180 degrees about an axis along its length, and maintainsthis angular orientation along its entire length of that radial section.This results in the corresponding wide surface of the ribbon on bothradial sections facing the same direction. This twist in the ribbonresults in the twist being entirely generated through 180 degrees at thecircumferential sections of the loop. Finally the two radial sectionsare placed so that they are radii of adjoining cylinders about the sameaxis. Stated another way, the circles of rotation of the two radialsections of the ribbon, develop two cylinders that are co axial andadjoining each other but do not intersect each other. This constructionof the loop allows a series of such loops to interlock with each otherto form a complete torroid or annullar ring without any gaps. Moreover,if the magnetic material is bonded to the ribbon this will form adistributed core as well. With this construction of interlockingribbons, the cross section of the torroid or annullar ring has tworibbon shaped conductors edge to edge one each fron the loops on eitherside of the torroid or annullar ring. Each of the independent loops haveterminals or simply flanges at each end of the ribbon loop positionedpreferably on the inner circumferential section. Such flanges may beconnected in series or parallel to each of the phases of the powercircuits, to meet the particular winding need. Such connections may bemade with pins that connect selected flanges.. Notably, such a windingcan be universal except for the sector angle that is described by theloops, in that the individual loops can be connected to any number ofphases and turns per winding. A further improvement would be to useconductors of widening cross section on the radial sections to maximizethe conductor crossection in each loop. The ribbon may alternatively betwisted by 360 degrees from end to end of the loop (instead of a net 0degrees) by twisting each of the circumfrantial sections by 180 degreesin the same direction (rather than in opposite directions for the 0degrees net). In either of these arrangements, the optimal utilizationof the stator winding volume is achieved by adjusting the thickness ofthe conductors in relation to the thickness of the ferromagneticmaterial to maximize the flux linkage to the rotor by lowering thereluctance with more ferromagnetic core material while maximizing theconductor thickness and the current density. The conductor ribbons maybe stranded and or braided wire to be more flexible in this arrangement.In some embodiments the entire back shaped as an annular flat diskbetween the two sections of conductors provides additional rigidity tothe windings but is not physically connected to the axle. The entireload is transferred through the material of the windings to the axle.The back iron may be radially serrated to accomodate the edges of thewindings and bonded together by methods well disclosed in the backgroundart. Moreover, if the stator windings are predefined at the time ofassembly and the physical angle of each phase winding is known inadvance, the back iron may have raised sections that index the windingsbetween these sections of the ribbon windings to transfer torque duringoperation. In addition the ribbon conductors may be shaped to index thesides of the back iron disk. In other embodiments several groups ofadjacent radial sections of the ribbon windings are selected insymmetric positions around the stator, and each of the radial ribbonsections in these groups are fabricated to have broader cross sectionsin the radial (or working) sections of the ribbons thereby creating aset of splines—one for each group, that face the back iron, and that mayinterlock with splines in the back iron to transfer torque.

[0107] The above winding arrangements utilize the entire space in thetorroid or annullar ring with either conductors or magnetic corematerial. Furthermore it is possible to “grind” the windings or ribbonsalong with the distributed core to have any desired cross section forthe stator thereby optimizing the airgap that may follow a non-linearrotor cross section as in some special rotor configurations noted inthis invention,

[0108] This embodiment has rotor disks with magnets that are tapered tobe narrower at the center and broader and the periphery where they areattached to the body of the rotating shell, and wherein the stator disksare tapered to be broader at the base at the axis and narrower towardsthe edge of the disks. Thereby the geometry will ensure that of thetaper rates are the same for stator and the rotor, the airgap willremain the same radially across the machine for all the disks. Moreover,as the greatest torsional forces on the stator are near the axis and thegreatest tortional forces on the rotor are near the periphery, thisgeometry can optimize material usage to minimize weight of the machinefor the required strength characteristics.

[0109] An additional feature of the present invention with the abovetapered rotor design can be utilized to optimize the air gap fordifferent speeds for operation. A small air gap is desired in themachine at low speeds to maximize the torque generated by the machine.However as the machine builds speed, both back EMF and air resistance inthe air gap will limit the speed of the machine significantly. Thetapered design in the present invention can be adapted to automaticallyincrease the air gap at high speed . This can be a smooth gradualprocess that matches the gap for the speed of performance. This isachieved by moving the sections of the rotor radially outwards by a verysmall amount. Notably, by having different gradients of taper of thesides of the rotor radially, the rate of change of the airgap can bedifferent for different radial distances from the axis. For example, asthe relative linear velocity between the stator and the rotor at theperiphery of the motor rises more rapidly as the motor accelerates, agreater increase in air gap could be beneficial at the periphery. Thiscan be achieved by having a steeper taper at the periphery of the motor(rotor and stator) and a more gradual taper towards the center of themotor. The exact tapers can be designed using computer simulations ofthe effect of back EMF and turbulent flow in the airgap. This movementmay be achieved with centrifugal force on the rotor sections and specialfabrication of the radial magnet sections (and brackets if used) of therotor and the intervening mechanical connectors that may be springloaded to permit slight expansion circumferentially and a specialconstruction of the rotor with the bearings on the axle to permit aslight extension radially. Such an arrangement can “stretch” the outersupporting ring of the rotor under centrifugal force to increase the airgap with the above tapered design. The outer supporting ring can havespring loaded telescoping sections between the magnet supports, thatallow this increase in diameter under centrifugal force. The magnets(with radial support brackets if used) may be connected rigidly at theouter periphery but slidably at the inner end to a ring support that maybe attached to a bearing that support the magnet assembly particularlywith regard to axial movement.

[0110] Yet another approach for changing the airgap is to utilize thetorque generated in the machine to stretch elements of the rotor. Forexample if the sectors of the rotor are constructed as radial sections(for example for each pole section separated physically) and supportedpivotally at the center and the external periphery by two annular ringsor other support (the inner supports must allow some movement as well:such as with an elongated slotted pivot ), such that when the sectionsare perfectly radial there is a larger gap between the radial elements(not the working airgap between the rotor and stator). A twisting of theinner annular ring about its axis, forces the “radial” magnet sectionsto move at a slight angle to the radial but increases the radialdistance at each point on the magnet from the axis by moving the slottedpivots slightly in their respective slots. Under low load and no-loadconditions the sectors of magnets are designed to be at a small angle tothe radial direction thereby increasing the working airgap as a resultof the tapered construction of the rotor and stators. However, underhigh load conditions the torque generated by the motor will drive themagnet sectors to a perfectly radial position thereby reducing theworking airgap and increasing the power delivered by the machine and thetorque generated against the load. The mounting arrangement will ofcourse have to be spring mounted to resist these changes at low torquebut allow this distortion at high torque. There should also be an endstop device to prevent the rotor sections from moving past the radialposition to incline from the radial in the opposite direction to theno-load position under extreme load and thereby reducing the ability ofthe machine to provide adequate torque as a result of the increase ofthe working air gap.

[0111] Another feature of this embodiment utilizes the fact that themagnets need to be supported to resist a tangential torque and a outwardradial centrifugal force while in operation. As the rotor is supportedin these embodiments by the motor body structure, the magnets in sectorsmay be fixed on the outer circumfrancial edge and radial air gaps (between radial sectors of magnets as distinct from the required axialair gap for operation) pemitted between adjoining magnets with onlyminimal support with spacers or minimal brackets to support the magnetsto equalize torque between the magnets and reduce vibration. Theseradial airgaps contribute to the cooling of the magnets—a particularlyimportant factor in axial gap machines. The cooling can be furtherimproved by inclining the magnet faces between the magnets to be at asmall angle to the axial direction so that the gaps scoop air from oneside of the rotor and deposit it at the other side of the rotor. The Airreturn path could be at the periphery of the motor where cooling devicesmay be harnessed to lower the temperature of the air. The Air that isforced through the motor may be retuned to the other side of the motorafter cooling in tubes on the periphery of the motor or inducted on oneside of the motor and discharged on the other side of the motor. Thelatter arrangement will benefit more from a low ambient temperature butsuffer from the disadvantage of impurities in the air that may damage orimpair the motor operation. Some embodiments for such cooling follow inthe present invention. Notably the stator windings in adjoining sectionsalong the axis will need to be sqewed to ensure that the faces of themagnet line up with the rotor windings on both sides for the rotor (inthe event of stator windings being present on both sides for the rotormagnet). Still other embodiments have the radial sections fo the magnetssubdivided into smaller radial sections and interspersed with insulationthin film and pinned together to form each of the magnets that comprisethe set of magnets around the perimeter of the rotor. This constructionwill reduce the Hall effect heating and power loss in the magnetassemblies.

[0112] Yet another feature of this invention is the use of a number ofoscillators that are each phase lagged to one another, the set of saidoscillators together forming a complete 360 degree phase shift and maybe driven off a controller (for example a hall effect controller) thatidentifies the position of the rotor for synchronizing the set ofoscillators. These oscillators are connected to each of the phases ofthe motor (or generator) The power angle, and frequency are controllablewith large capacitors ( ultra capacitors may be used in thisapplication) thereby permitting control of power delivered or extractedin regenerative mode of the motor. This arrangement of the sequence ofoscillators provide a mechanism for energy storage, deployment andretrieval in the short term particularly useful in vehicle driveapplications. The oscillators can be designed to deliver sinusoidalwaveforms or even what may approach square wave forms to maximize thetorque generation of each phase. The background art has extensivematerial related to the use of controllers and sensors for control ofmoving magnet rotor motors, in the design of phase lagged systems ofoscillators and power control of electrical machines by changing thepower angle and frequency control of electrical oscillators. Notably thetorque generation of the motor may accelerate the motor that in turnwill require a higher frequency of oscillator output. To continue torquegeneration.

[0113] Yet another feature of the present invention has separate loadbearing axial bearings for the wheel from the bearings of the motor,while the wheel and motor are coupled to convey torque along theperiphery of the motor, thereby minimizing the radial compression of themotor due to loads that the vehicle bears and which are transmittedthrough the wheel bearings. This will improve the performance of thetapered design for the motor elements as noted above by minimizing thechange in axial gap with physical loads on the vehicle and its wheels.

[0114] Special arrangements need to be made in this and otherarchitectures if there is a load supporting function for the presentinvention as in the use in a wheel structure for a vehicle. Load bearingfunctions as in wheels particularly on uneven surfaces, will causerelative compression of the rotor relative to the stator in the regionbelow the machine, if there is a rigid connection between the wheel andthe motor. Furthermore the unsprung mass of the wheel can be substantialif the motor is rigidly connected to the wheel. An alternativearchitecture proposed in the present invention will be to have the loadbearing bearings of the wheel separate to those of the motor itself andthe motor shell attached flexibly to the wheel periphery to transfertorque. This may be done with tangential leaf springs that around theperiphery mounted at one end to the wheel and at the other end to themotor housing on its periphery and thereby indirectly attached to therotor. In this arrangement for forward motion the leaf springs will bein tension. These leaf springs may be designed to accommodate acompressive load for reverse motion of ht e vehicle. Alternatively, asecond set of leaf springs may be used to be in tension when the vehicleis reversing and in compression in the forward direction. This secondset of leaf springs may also be mounted at one end to have limitedsliding capability so that when the vehicle is moving forward, thesesprings are not in compression but slide at the end coupling, but slideback to accept the tensile load when the vehicle is in reverse. Thislimited sliding arrangement may also be done for the first set of leafsprings to avoid compression when the vehicle is in reverse.

[0115] Another approach for the torque conversion in this architectureis to have key and slot arrangements along the periphery between thewheel and the motor. Compression of the wheel at any point on itsperiphery can be accommodated by the key sliding further into the slot.Torque will be transferred by the keys. The arrangement may have theslots on the wheel and the keys on the motor housing or with the slotson the motor and the keys on the wheel.

[0116] This new architectural feature may be taken further to haveinternal shock absorption for the wheel with flexible elements betweenthe wheel bearing and the wheel periphery, thereby protecting the motorfrom excessive shock in this application as a wheel motor and reducingfurther the unsprung mass of the wheel. For example heavy leaf springscan be mounted tangentially between the periphery of the wheel and thecentral part of the wheel that is connected to the bearing, these leafsprings will accommodate some deflection of the wheel periphery relativeto the bearing. In some embodiments of such internal shock absorbtionfor wheels magnetic bearings may be employed.

[0117] Another aspect of the present invention is that cooling of themachine can be achieved with one or more of the following means:

[0118] 1. In applications where the motor operates in dusty conditionsor in water, the motor may be cooled with air pumped through an axialhole in the axle of the motor through ports in the stator between therotor sections and forced out of the ports in the rotor. He pressuredifference can be designed to ensure that there is no water or dustentering the motor.

[0119] 2. In less severe conditions the motor casing can have fins verymuch like brake fins ion car wheels that scoop air into the motorthrough ports in the outer rotor disks each of the rotors and the statordisks inside the machine.

[0120] 3. Yet another approach is to use bimetallic conductor strips ineach of the loops of ribbons that are proposed in the windings such thata part of the loop is of one metal and the remaining part of that loopis of the other metal, thereby forcing a cool junction at the peripheryof the motor. The hot end can be designed to the axle which can bedesigned to be a heat sink to conduct heat to outside the motor. Such Itheat dissipation at the axle may be improved with water or other coolantcirculation through the axle using techniques well disclosed in thebackground art. This arrangement can be combined with that descriebedearler with the rotor magnets with the inclined radial air gaps betweenthe sector magnets, scooping air from the axial gap on one side of therotor and depositing it on the other side and forcing a pressuredifferntial that drives the air over the periphery of the stator whichis cooled using the cold junction. The air may be returned along sealedpaths or inducted and discharged to the atmosphere on the sides of themotor. If inducted and discharged into the atmosphere it will benefitadditionally from the lower ambient air temperature. The hot junctionwill be at the axis, and the axle may be designed to be a heat sink toconduct heat out of the motor. In these embodiments that use thebimettalic stators for cooling there will of course be a direct currentsuperimposed on the reversing currents (if required) to provide thecooling effect. The bimettalic winding arrangement may also beconstructed to have the cold junctions and hot junctions in differentlocations, but such arrangemtns need to have heat sink arrangements nearthe hot junctions and locate the cold junctions where the magnets arecooled directly by convection through the air gap or cooled by an airflow that is forced around the cold junction. For example someembodiments may have the cold junction at the axis of the stator andfins at the periphery of the rotor to cool the outer edge of the airgapwhere the hot junction is located. Air can be forced through ports inthe stator near the axle. And continue through the gaps between themagnet assembles to cool the magnets. Returns paths or induction andexhaust routes for the cooling air may be used as noted for the abovedesigns. Gases other than air may be used to increate thermal capacityfor heat removal from the magnet structure. By using the foregoingtechniques, an electric machine can be fabricated with improvedefficiency and results in an electric machine having improved operatingcharacteristics.

[0121] Considering that in an application of the present invention in avehicle wheel, ease of removal of the wheel and he motor are keybenefits, the present invention proposes a central attachment along thenon rotating axle for attachment with a central bolt that secures thewheel to the axle. The fit of the axle with the wheel socket for thispurpose, may be tapered to allow the tension in the bolt to increase thereaction force between the socket and the axle surface. Moreover, totransfer torque the socket and the axle contact surfaces may be splinedor keyed.

[0122] Furthermore this possible assembly aspect of the presentinvention may be other refined to have the wheel in two sections—theiner section that is on one side of the motor on the axle and outersection that is on the other side of the motor on the axle. Removal ofthe wheel without removal of the motor may be facilitated by removal ofthe external section only with the tire. The two sections of the wheelmay be held together under operating conditions by bolts or otherfasteners or simply key into each other when the rim and tire with theexternal section are installed to the axle. This keying arrangement mayalso be between the wheel rim attachments and the inner section.

[0123] Alternative Embodiments

[0124] In an alternative embodiment to the preferred embodiment, thestator winding construction uses stampings that form the entire circleof rotation of the motor. Apertures are stamped out for the magneticcore material that also forms support and each leg of the winding hasconfiguration to provide the required flux generation to the coreelements. The stampings are interleaved with thin insulating sheets, andmay be displaced by a desired angle from the preceding stamping. Tocomplete the winding design, pins may be inserted through the stack ofstampings. Those stamping layers that need to be connected to each otherwill have a tight fit with two or more pins. Those that belong toanother set of windings or phases have a loose fit to the pin in thatlocation thereby not allowing electrical contact, but having otherlocations where the pins have a tight fit to form the requiredelectrical contact. Notably the holes that match up with the pins may bestamped out as well and are designed to be narrow for the pins that needto be connected for the relevant stamping and wide for the pins thatshould not be connected to the relevant stamping. This design can beused for a wide variety of winding designs. Finally in these embodimentsconductor thickness can be increased by utilizing space in the plane ofstampings that do not have conductors in a particular winding radialsection, by building up the adjoining stamping that does have aconductor in that particular winding section or radial section.

[0125] Another alternative embodiment of the windings using thetorroidal structure with ribbon conductors can use braided or strandedmaterial for the conductor. Yet another embodiment of the toroidalstructure of the windings will have sheet metal stamped and bent intothe required shape of each turn of the windings. These can be stamped tohave flanges for connecting pins as well on the outer or inner peripheryas well.

[0126] In yet other embodiments, the ribbon conductors may be eitherslotted on the inside circumfrancial sections or bent around (at thesections of the ribbon that is twisted, at a point where the width isparallell to the radius) to accommodate radial support elements of theback iron linked to the axle, that may lie between the concentriccylinders formed by the windings as noted above.

[0127] Yet another embodiment will have the ribbon conductors packedwith powder metal and compacted with dynamic magnetic compaction orother techniques available in the background art. This will improve theefficiency of utilization of space between conductors for a lowerreluctance magnetic path. This is particularly useful if a constantthickness conductor is used and there is a greater gap between adjoiningconductors towards the outer end of the working conductors. Yet anotherfeature of this invention is an embodimen that has the radial sectionsofeach ribbon conductor preformed and attached to a (insulating) membranebag of the same shape as a side of each of the radial sections of theconductor, containing powder metal in a predetermined quantity. At thetime of assembly of the coil, the powder metal will be redistributed inthe thin membrane bags to take up all the available spacebetween theconductors—more towards the outer ends of the radii. The assembly maythen be compacted as noted above. Following the assembly of the windingsas follows, the surface of the winding with the attached core materialmay be ground or machined to expose the surface of the ribbon conductorfrom the surrounding core material so that a magnetic gap is establishedto inimize magnetic leakage in the machine.

[0128] Several alternative embodiments of this invention are possiblewith the windings in the current invention using topologicallyequivalent conductor shapes. For example individual ribbon loops may beconstructed to have two flanges near the axial edge of the workingconductors on each of the legs of the loop, so that in the windingposition these flanges of adjoining loops form a ring around the axis ofthe machine that can be used for support and also heat dissipation ifthey engage fixed elements of the axle. Moreover, such flanged may bearranged to be of varying lengths such that when assembled as a windingthey form a splined profile that will better transfer torque to the axlewhich may have support flanges appropriately splined. Anotherapplication in using topologically equivalent conductors to flat ribbonconductor loops is to fold the conductor at the non-working ends toreduce the edge length on one side and not the other so as to alloweasier assembly of the the loops in the stator torroid. Yet anothertopologically equivalent form is to have an“O” shaped flat ribbonconductor (that may be stamped out) with straight sides that correspondwith the length of the working conductors of the loop and straightconductors of the length of the non-working peripheral and axialconductors respectively. The closed form needs to be cut and separatedat a point on the inner non-working conductor section to connect withadjoining loops. Sections of the Non-working conductors can then be bentto be perpendicular to the working conductors to permit the loop andwinding configuration of the twisted conductor torroid constructionnoted in this invention with one notable difference—The torroidgenerated by these open loops that form the windings may not have anaxis perpendicular to the width of the conductor but be at an anglethereby compromising he eddy current loss characteristics and theairgap.

[0129] Yet another embodiment uses the torroidal coil arrangement asdescribed but with the permanent magnet rotor fixed to the axle and thestator attached to the housing of the machine.

[0130] Yet another alternative embodiment of the windings in thetorroidal structure above has wound coils shaped into rectangularsections (it will no longer be necessary to minimize the Hall effect ofthe conductors and therefore the thickness of the coils can becomparable to the width of the coil. Each of the coils would theninterlock to form a torroid or annullar ring. Each radial limb of thecoil may have magnetic material attached to it to form a distributedmagnetic core.

[0131] Yet another embodiment can use differential expansion of therotor with regard to the stator to increase the airgap at highertemperatures with the tapered design in the present invention. Each ofthe magnet structures that are positioned radially are connectedtogether circumfrantially and to the hub in the center by materials thathave a high coefficient of expansion with heat in addition to theirrequired load bearing properties required in this application. As thetemperature of the machine rises the expansion on the rotor of theconnecting elements between the magnets and the connecting elements tothe hub(s) is designed to exceed that of the expansion of the stator andas result of the tapered construction will cause an increase in the gapof the machine.

[0132] Yet another embodiment has “radial” airgaps between the magnetstructures in the magnet assembly of the rotor, constructed to have aslight angle to the radial direction and said gap having a small angleto the axial direction on each side facing a working airgap, threbyproviding a mechanism to scoop air out from the working airgaps anddischarge the hot air though ports at the periphery of the machine. Theairflow can also be reversed in a similar embodiment where air isscooped up through ports on the periphery of the machine and pumped outto the working air gap. Such air can be exhausted through ports in theaxle or at the periphery of machine between the magnet assemblies.

[0133] Yet another embodiment of this invention has a magnet rotorattached to the axle with the stator attached to the housing andcomprisig windings with a higher coefficient of expansion than themagnet assemblies, thereby increasing the air gap with the taperedrotor/stator arrangement.

[0134] Another alternative embodiment has the rotor of a multi-rotormachine with interspersed stators, entirely supported by the housing ofthe motor and without bearings at the axle between stators for therotors, thereby reducing cost and weight of the machine.

CONCLUSIONS, RAMFCATIONS & SCOPE

[0135] Thus it will become apparent that the present inventionpresented, provides a new paradigm for the design of electrical machinesfor the use in wheel motors and other applications where high torque andlow mass are required. The present invention presents embodiments thatmake these applications achievable with a unique machine structure,fabrication techniques and thermal, electric and magnetic performancemanagement.

1. (I) In an axial gap machine having a permanent magnet rotor and astator comprising windings and a working airgaps between said statorsand rotors, such that movement of the magnets and their magnetic fieldrelative to the windings in the stator generate an electromotive forceacross the windings and conversely such that when there is anelectromotive force applied to the ends of the windings, the inducedcurrent in the windings and thereby in the magnetic field of the magnetsin the rotor, create a force on the magnets of the rotor to cause itsmovement in a predetermined direction of rotation, a means to controldelivered torque of the machine under an applied electromotive force tothe windings by changing the working air gap of said electrical machine,using a matched tapered geometry for the rotors and stators of saidmachine such that radial outward movement of elements of the rotorrelative to the stator increases the working airgap of said electricalmachine.
 2. (D) An axial gap machine as in claim 1, wherein said changein torque output by said machine is achieved by a change in thetemperature of said machine windings of the stators and machinepermanent magnet rotors by a predetermined relative movement of therotor outwards radially with regard to the stator as a result of adifference in the thermal expansion of the rotor magnet supports wthregard to the stator windings:
 3. (D) An axial gap machine as in claim1, wherein said change in torque output by said machine is achieved by achange in the load applied to the machine rotor by an angular movementof the rotor magnet sectors each relative to a pivot at their support onthe outer radial end to align with the radial direction under load, suchangular movement being facilitated by a support at the inner end of saidmagnet sectors that holds said magnet sectors slidably and pivotally,said magnet sector mounts being spring loaded to maintain a no-loadposition of said magnet sectors at a slight angle to the radialdirection.
 4. (D) An axial gap machine as in claim 1, wherein saidchange in torque output by said machine is achieved by a change in theangular velocity of the rotor and the resulting centrifugal force actionon the rotor by a extension of spring loaded magnet supports on theinner side of said magnet assemblies facing the bearings and a extensionin the supports of the magnet assemblies between said magnet assemblieswich are spring loaded to resist such extension under static conditions,thereby moving the magnet assemblies with tapered cross sectionsradially outwards under high angular velocity of said rotor, resultingin an increase in the air gap.
 5. (D) An axial gap machine as in claim1, further comprising a winding arrangement for one or more statorswherein the working conductors are symmetric with regard to both theaxis of rotation of the rotor, and a plane orthogonal to the axis ofsaid machine and wherein the radial half plane parallel to the axis andintersecting the axis, on rotation about the axis intersects at most,two working conductors each of monotonically decreasing width withincreasing radial distance from the axis, said conductors havingsubstantially equal thickness, and wherein said width of said conductorsis much larger than said thickness of said conductors to minimize Halleffect losses.
 6. (I) In an axial gap machine having a permanent magnetrotor and a stator comprising windings and a working airgaps betweensaid stators and rotors, such that movement of the magnets and theirmagnetic field relative to the windings in the stator generate anelectromotive force across the windings and conversely such that whenthere is an electromotive force applied to the ends of the windings, theinduced current in the windings and thereby in the magnetic field of themagnets in the rotor, create a force on the magnets of the rotor tocause its movement in a predetermined direction of rotation, a means toprovide lateral support for the rotor sections and the stator sectionsby using a matched tapered geometry for the rotors and stators of saidmachine.
 7. (I) In an axial gap machine having a permanent magnet rotorwith a plurality of poles, and a stator comprising windings and aworking airgaps between said stators and rotors, such that movement ofthe magnets and their magnetic field relative to the windings in thestator generate an electromotive force across the windings andconversely such that when there is an electromotive force applied to theends of the windings, the induced current in the windings and thereby inthe magnetic field of the magnets in the rotor, create a force on themagnets of the rotor to cause its movement in a predetermined directionof rotation, a winding arrangement to utilize the entire stator surfaceadjoining the annular working airgap of said electrical machine with atmost two working conductors along any radial half plane through the axisof rotation of said machine, deployed to provide a continuously variablenumber of turns per winding and corresponding number of overlappingwinding phases per pole. 8.(I) In an axial gap machine having apermanent magnet rotor with a plurality of poles, and a statorcomprising windings and a working airgaps between said stators androtors, such that movement of the magnets and their magnetic fieldrelative to the windings in the stator generate an electromotive forceacross the windings and conversely such that when there is anelectromotive force applied to the ends of the windings, the inducedcurrent in the windings and thereby in the magnetic field of the magnetsin the rotor, create a force on the magnets of the rotor to cause itsmovement in a predetermined direction of rotation, a winding arrangementfor one or more stators wherein the working conductors are symmetricwith regard to both the axis of rotation of the rotor, and a planeorthogonal to the axis of said machine and wherein the radial half planeparallel to the axis and intersecting the axis, on rotation about theaxis intersects at most, two working conductors each of monotonicallydecreasing width with increasing radial distance from the axis, saidconductors having substantially equal thickness, and wherein said widthof said conductors is much larger than said thickness of said conductorsto minimize Hall effect losses.
 9. In an axial gap machine as in 8,wherein said working conductors are closely packed to maximize theconductor volume that may utilize the magnetic field in the airgap forthe operation of said machine.
 10. In an axial gap machine as in 8,wherein said stator windings are machined following assembly of saidstator, to conform to a predefined cross section profile, therebyfacilitating better airgap tolerances of the machine when in operation.11. In an axial gap machine as in 8, wherein said working conductors arebonded to insulated magnetic core elements of length equal to the widthof said working conductors, and oriented in a direction parallel to theaxis of rotation of said machine, said core elements having relativelysubstantially smaller width and thickness, thereby minimizing eddycurrent losses in said core elements.
 12. A stator of an axial gapmachine comprising working conductors and insulated magnetic corematerial bonded thereto as in 11, wherein said stator cross section atdifferent radial distances from the axis is machined to a predefinedcross section after assembly.
 13. In an axial gap machine as in 8,wherein said working conductors are packed with powdered magnetic corematerial and thereafter, compacted and bonded to said workingconductors, thereby providing low reluctance in the core magneticmaterial but high electrical resistance to minimize eddy current lossesin said magnetic core material.
 14. A stator of an axial gap machinecomprising working conductors and powdered magnetic core materialcompacted and bonded thereto as in 13, wherein said stator cross sectionat different radial distances from the axis is machined to a predefinedcross section after assembly. 15.(I) A Method for winding a statorcomprising: Assembling a plurality of conductor loops, each shaped tohave a twist on each of the non working sections and each equipped withend connection arrangements to attach to adjoining loops in apredetermined way; Packing said assembled winding with powdered corematerial; Compacting said assembled winding packed with powdered corematerial; Attaching said assembled windings to the axle of said machine;Grinding or otherwise machining said stator assembly to meet apredefined cross section; Thereby building a stator assembly that willmatch a permanent magnet rotor assembly of said electrical machine. 16.(I) A Method for winding a stator comprising: Assembling a plurality ofconductor loops, each shaped to have a twist on each of the non workingsections and each equipped with end connection arrangements to attach toadjoining loops in a predetermined way and each bonded on its workingconductor sections with core material in thin strands of predeterminedcross section oriented in length across the width of said workingconductors and bonded to said working conductors; Attaching saidassembled windings to the axle of said machine; Grinding or otherwisemachining said stator assembly to meet a predefined cross section;Thereby building a stator assembly that will match a permanent magnetrotor assembly of said electrical machine.
 17. (I) In an axial gapmachine having a permanent magnet rotor and a stator comprising windingsand a working airgaps between said stators and rotors, such thatmovement of the magnets and their magnetic field relative to thewindings in the stator generate an electromotive force across thewindings and conversely such that when there is an electromotive forceapplied to the ends of the windings, the induced current in the windingsand thereby in the magnetic field of the magnets in the rotor, create aforce on the magnets of the rotor to cause its movement in apredetermined direction of rotation, said permanent magnet rotor furthercomprising a circular array of magnet structures comprising the magnetassembly, a means to cool the magnet assembly in the said permanentmagnet rotor by arranging the magnet pole pairs around the periphery ofthe rotor, with radial gaps between them to allow airflow, said magnetsbeing supporting on their outer radial periphery against centrifugalforces and minimal support elements between magnet assemblies to allowsaid airflow.
 18. A permanent magnet rotor comprising magnet structuresin a magnet assembly of an axial gap machine as in 17, wherein saidradial gaps between said magnet structures are inclined to the axis ofrotation such that on rotation of said rotor in said electrical machine,said radial airgaps act as air scoops to pump air from one side of therotor to the other thereby contributing to forced air flow for cooling.19. A permanent magnet rotor comprising magnet structures in a magnetassembly of an axial gap machine as in 17, wherein said “radial” gapsbetween said magnet structures are slightly inclined to the radialdirection, and inclined in the same direction to the axis of rotation onboth their edges adjoining the working air gap such that on rotation ofsaid rotor in said electrical machine, said radial airgaps act as airscoops to pump air from both sides to the periphery of the rotor forexhaust through ports in the housing of said machine therebycontributing to forced air flow for cooling of said magnet assembly. 20.A permanent magnet rotor comprising magnet structures in a magnetassembly of an axial gap machine as in 17, wherein said “radial” gapsbetween said magnet structures are slightly inclined to the radialdirection, and inclined in the same direction to the axis of rotation onboth their edges adjoining the working air gap such that on rotation ofsaid rotor in said electrical machine, said radial airgaps act as airscoops to pump air from ports in the housing through the “radial” airgapto both sides of the rotor adjoining the working airgap, therebycontributing to forced air flow for cooling of said magnet assembly. 21.(I) In an axial gap machine having a permanent magnet rotor and a statorcomprising windings and a working airgaps between said stators androtors, such that movement of the magnets and their magnetic fieldrelative to the windings in the stator generate an electromotive forceacross the windings and conversely such that when there is anelectromotive force applied to the ends of the windings, the inducedcurrent in the windings and thereby in the magnetic field of the magnetsin the rotor, create a force on the magnets of the rotor to cause itsmovement in a predetermined direction of rotation, said permanent magnetrotor further comprising a circular array of magnet structurescomprising the magnet assembly, a means to reduce eddy current losses insaid magnet structures by composing each of said magnet structures withradial magnet elements bonded or pinned together such that each magnetstructure has a plurality of magnet elements adjoining each other in acircumfrancial direction and having the same thickness in the axialdirection at any radial distance from the axis.
 22. (I) In an axial gapmachine having a permanent magnet rotor and a stator comprising windingsand a working airgaps between said stators and rotors, such thatmovement of the magnets and their magnetic field relative to thewindings in the stator generate an electromotive force across thewindings and conversely such that when there is an electromotive forceapplied to the ends of the windings, the induced current in the windingsand thereby in the magnetic field of the magnets in the rotor, create aforce on the magnets of the rotor to cause its movement in apredetermined direction of rotation, a means to cool the magnetstructure using a bi metallic construction for the stator windings, suchthat a currnet flowing through the bimetallic loops induce a temperaturechange between the junctions of the two metals creating a hot junctionand a cold junction, thereby providing a cold junction that may be usedto cool the air in the airgap and by convection, cool the magnet isstructure, said hot junction being cooled by means external to theelectrical machine. 23.(I) An axial gap machine having a permanentmagnet rotor and a stator comprising multiple phase windings and aworking airgaps between said stators and rotors, such that movement ofthe magnets and their magnetic field relative to the windings in thestator generate an electromotive force across the windings andconversely such that when there is an electromotive force applied to theends of the windings, the induced current in the windings and thereby inthe magnetic field of the magnets in the rotor, create a force on themagnets of the rotor to cause its movement in a predetermined directionof rotation, further comprising a set of occillators each lagged by aphase angle to the next occilator and powered by a electrical source anddesigned to power each of said phase windings with a relative phase lagbetween adjoining phase windings, and further designed to have anaggregate phase shift of up to three hundred and sixty degrees, therebyproviding the electrical machine with a suitable multiphase power sourcefor operation.
 24. (D) An axial gap machine powered by a system of phaselagged ocilators as in 23, wherein each of said occilators areconstructed with ultracapacitors to store electrical energy.
 25. (D) Anaxial gap machine powered by a system of phase lagged ocilators as in23, wherein each of said occilators are designed to provide a variablepower angle to permit said electrical machine as a motor or as agenerator.
 26. (I) A wheel motor and wheel assembly wherein said wheelhas separate bearing supports about the axis of rotation with regard tosaid wheel motor such that radial impacts on said wheel while inoperation do not directly impact said wheel motor and thereby does notcause radial distortion in the axial direction of said wheel motor, saidwheel motor transferring torque to said wheel through a plurality ofleaf springs in tension arranged around the periphery of said wheelmotor and located between said wheel motor and said wheel.
 27. (I) Awheel motor and wheel assembly wherein said wheel has separate bearingsupports about the axis of rotation with regard to said wheel motor suchthat radial impacts on said wheel while in operation do not directlyimpact said wheel motor and thereby does not cause radial distortion inthe axial direction of said wheel motor, said wheel motor transferringtorque to said wheel through a plurality of splines on the outer casingof said wheel motor engaging a plurality of splines arranged around theinside of said wheel, such that when engaged said splines engage one ofthe lower side of the wheel or the upper side of said wheel, therebyensuring that vertical upward impact forces on the wheel result in thepairs of splines engaging either deeper or shallower respectively.